Battery compartments for housing batteries used in powering various electronic devices such as night vision goggles, flash lights, camera light meters, etc., are well known in the art. Such battery compartment designs include removable battery compartment caps which enable the battery or batteries contained within the compartment to be removed and replaced with a new or recharged battery or batteries.
Referring to FIG. 1A, there is shown a AN/PVS-7B night vision goggle device 58 (illustrated by the dotted lines) which includes a horizontally oriented PVS-7B battery compartment 50 closed by a removable prior art PVS-7B battery compartment cap 10. The battery compartment cap is tethered to the night vision goggle device by a retainer strap 57. As can be seen in FIG. 1C, the battery compartment 50 is loaded with either Lithium Sulfur Dioxide BA-5567/u batteries 52 (only one is shown) or two (2) AA batteries.
FIG. 1B is an exploded perspective view of the removable battery compartment cap 10 of FIG. 1A. As shown, the battery compartment cap 10 generally comprises a cap member 12, the retainer strap 57, a retainer link 59, an o-ring 48 and a contact assembly 28. The cap member 12 includes a circular top 14 and an annular skirt 24 depending from the periphery of the circular top 14. The compartment side surface of the circular top 14 includes a centrally disposed contact locating post 16 surrounded by an annular contact seating flange 18 and a circumferential lip 20. The circumferential lip 20 in conjunction with the annular skirt 24 define a groove 22 for receiving the o-ring 48 that seals the battery compartment cap 10 to the battery compartment 50. The exterior surface of the circular top 14 defines a centrally disposed projection 15 with an enlarged end 17 for coupling the battery compartment cap 10 to the retaining strap 57. The retaining strap 57 is coupled to the night vision goggle device 58 by a retainer link 59. A thread arrangement 26 for securing the battery compartment cap 10 to the battery compartment 50 is provided on the inner surface of the annular skirt 24.
Still referring to FIG. 1B, the contact assembly 28 includes a stamped metal contact 30, a washer 38, a circular retaining clip 40 and a conical-shaped coil spring 42. The contact includes a hub 32 portion with a centrally disposed aperture 33. Three spoke members 34 extend radially from the periphery of the hub portion 32. In between any two of the three spoke members is a tab 36. Each tab 36 extends axially in the direction of the spring 42 from the periphery of the hub portion 32. The circular retaining clip 40 that retains the contact 30 to the contact locating post 16 includes sharp projections 41 which cut into the locating post 16. The coil spring 42 includes a large diameter end 44 and a small diameter end 46.
Each component of the contact assembly 28 must be separately assembled to the cap member 12 as follows. First, the contact 30 of the contact assembly 28 is assembled to the cap member 12 so that the hub 32 portion engages the annular seating flange 18 while the contact locating post 16 extends through the aperture 33 of the hub portion 32. Next, the washer 24 is installed onto the contact locating post 16 so that it rests against the hub portion 32 of the contact 30. The retaining clip 40 is then press-fitted to the contact locating post 16. Additional retention is sometimes provided by heat staking the free end of the contact locating post 16 after the retaining clip 40 is press fitted thereto. Finally, the coil spring 42 is non-removably secured to the contact 30 by the three tabs 36. This is accomplished by bending each tab 36 around a portion of the first coil of the large diameter end 44 of the coil spring 42 to mechanically secure the coil spring 42 to the contact 30. Then, each tab 36 is soldered to the coil to ensure electrical continuity between the coil spring 42 and the contact 30.
A completed electrical circuit is provided when the battery compartment cap 10 is installed on the battery compartment 50 loaded with batteries 52 as shown in FIG. 1C. The electrical circuit is created by the mechanical and electrical contact between the small diameter portion 46 of the coil spring and the negative end of the battery 52, and the solder connections between the coil spring 42 and the contact 30. The circuit is completed by the physical touching of the contact 30 to a ground sleeve 54 in the battery compartment 50.
Although the battery compartment cap 10 of FIGS. 1A-1C operates in a generally satisfactory manner, there exists certain disadvantages which reduces its utility. One disadvantage is that the contact assembly 28 is comprised of four (4) separate components which must be assembled in a process which involves three bending operations and three soldering operations which add complexity to the manufacturing of the battery compartment cap 10. Another problem with the battery compartment cap 10 is that it presents difficulties when the batteries 52 are changed. More particularly, when the battery compartment cap 10 is applied to the battery compartment, the relatively long free length of the uncompressed coil spring 42 (represented in FIG. 1C as dotted lines) causes it to contact the battery 52 before the thread 26 of the battery compartment cap 10 engages the thread 56 of the battery compartment 50, thereby requiring a significant compression force to apply the battery compartment cap 10. This causes difficulty when changing batteries, especially under adverse circumstances. Still another problem with the above design concerns the possibility of missed contact when loading certain types of batteries. In particular, certain types of batteries have diameters which are significantly small than the diameter of the battery compartment. If such batteries are loaded into the battery compartment when the battery compartment is oriented horizontally, the batteries tend to sit in an off-centered manner within the battery compartment. Consequently, when the battery compartment cap is applied to the battery compartment the small diameter end of the spring may not contact the batteries.
It is, therefore, a primary object of the present invention to provide an improved battery compartment cap with a one-piece contact assembly that substantially overcomes the disadvantages associated with prior art battery compartment caps.